Multi-layered opitcal data records and playback apparatus

ABSTRACT

Multi-layered optical data records and playback apparatus are described in which a plurality of optical data layers are provided on at least one side of a record substrate and the playback apparatus scans data tracks on such layers with a light beam to produce an electrical readout signal corresponding to the data in the scanned tracks. The playback apparatus includes selection means for selectively playing back data tracks on different ones of the data layers. The data track may be formed by lines of data spots of binary coded digital information or such spots may be frequency modulated or pulse length modulated analog information which are photographically recorded at extremely high data density so that they may be used to record audio or video signals including television signals. While the optical data records may be light transparent, they are preferably light reflective so that the playback light source and associated focusing and scanning means may be supported on the same side of the record as the light detector to provide a more compact playback apparatus. This also enables at least some of the same optical elements to be used for transmitting the reflected light beam to the detector that are used for transmitting the playback light beam from the light source to the record. Selection of one data track for playback may be accomplished by changing the focus of the light beam from one data layer to another, or by making the data tracks of optically different materials, such as using different color dyes or different photoluminescent materials, and selectively positioning corresponding color filters in front of the light detectors.

REFERENCE TO RELATED PATENT APPLICATION

This is a continuation of application Ser. No. 516,453, now abandoned,filed Oct. 21, 1974, which is a continuation-in-part of application Ser.No. 375,336, filed July 2, 1973 by J. T. Russell now U.S. Patent No.3,891,794.

BACKGROUND OF THE INVENTION

The subject matter of the present invention relates generally tomultiple layer optical data records and associated playback apparatus,and in particular to such records which include a plurality of datainformation tracks in different data layers provided on at least oneside of the record substrate or base member, and to such playbackapparatus which includes selection means for selectively reading out oneof such data tracks with a scanning light beam to produce an electricalreadout signal corresponding to the data on the scanned track. Themulti-layered records and playback apparatus of the present inventionare extremely useful for high density information storage. For example,one application of the present invention is the recording and playingback of audio and video signals used in television programs.

Previously it has been suggested in U.S. Pat. No. 3,430,966 of D. P.Gregg, granted Mar. 4, 1969, and U.S. Pat. No. 3,518,442 of K. O.Johnson, granted June 30, 1970, to provide an optical data record inwhich data is recorded by notches in two tracks on opposite sides of alight transmissive substrate member. However, such prior art records andtheir associated playback apparatus have several disadvantages since therecords only have one data layer per side and are read out bytransmitting a light beam through the record including a light diffusinglayer provided between the two data layers. As a result, these recordscannot store as much data as the record of the present invention and aremore expensive and difficult to manufacture. Also, the playbackapparatus requires separate focusing optical systems for the lightdetector and for the light source because they are on opposite sides ofthe record. Thus, the playback apparatus is not as compact as theembodiment of the present invention employing reflective records becausein the latter the detector is positioned on the same side of the recordas the light source.

It has been proposed by K. Compaan and P. Kramer in Philips TechnicalReview, Volumne 33, pages 178 to 180, 1973 No. 7, to employ lightreflecting optical data records so that the detector and light sourcemay be positioned on the same side of the record and may use commonoptical elements. However, this record has the disadvantage that opticaldata is recorded as pits or notches in a single layer which is formed ina conventional manner by pressing the records from a master. As aresult, only about thirty minutes of television programs can be recordedon a large record of 30 centimeters in diameter, the size of aconventional long playing phonograph record. The entire surface of therecord, including the data pits, is coated with metal for reflecting thelight beam so that several data layers could not be recorded on the sameside of the record in the manner of the present invention. The datapits, unlike the background surface, reflect the light beam away fromthe detector and are detected by the absence of light at the detector sothat there is a lower signal to noise ratio in the electrical readoutsignal than that of the present invention.

Also of interest as a background on optical data records and playbacksystems for fixed records in U.S. Pat. No. 3,501,586, granted Mar. 17,1970, to J. T. Russell. However, this patent does not disclosemulti-layered data records in the manner of the present invention.

SUMMARY OF THE INVENTION

It is, therefore, one object of the present invention to provide animproved optical data record of higher storage density having aplurality of data tracks recorded in different data layers on at leastone side of the record substrate.

Another object of the invention is to provide such a multi-layered datarecord of simple and economical construction which is provided withoptical data tracks of high accuracy without forming pits or grooves inthe record surface.

A further object of the invention is to provide such a multi-layereddata record of light reflective material so that it may be played backby using a light source and detector positioned on the same side of therecord and using at least some of the same optical elements to provide amore compact and less expensive playback apparatus.

Still another object of the present invention is to provide such arecord in which the light reflected from the data spots is detected toproduce an electrical readout signal of high signal to noise ratio.

An additional object of the present invention is to provide an improvedplayback apparatus including a selection means for selectively playingback the data tracks on different data layers provided on such amulti-layered data record.

Another object of the invention is to provide such a playback apparatuswhich selects the data tracks to be played back by changing the focus ofthe readout light beam from one track to another in a simple, accuratemanner.

A still further object of the present invention is to provide such animproved playback apparatus and record in which the data tracks areselectively played back by providing the data layers with differentoptical properties and detecting only light with the optical property ofthe selected data track.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will be apparentfrom the following detailed description of the preferred embodimentsthereof and from the attached drawings of which:

FIG. 1 is a schematic diagram of one embodiment of a playback apparatusfor a reflective type of multi-layer optical data record in accordancewith the present invention;

FIG. 2 is an elevation view taken along the line 2--2 of FIG. 1;

FIG. 3 is a schematic diagram of a second embodiment of a playbackapparatus similar to that of FIG. 1 but modified for light transmissivetype multi-layer optical data records;

FIG. 3A is an elevation view taken along the line 3A--3A of FIG. 3.

FIG. 4 is an enlarged section view of a portion of a multi-layer opticaldata record with spacer layers between the data layers which may be usedin the playback apparatus of FIGS. 1 or 3;

FIG. 5 is an enlarged section view of a portion of another embodiment ofthe multi-layer optical data record of the present invention with areflection layer separate from the data layers;

FIG. 6 is an enlarged section view of a portion of a third embodiment ofa multi-layer optical data record without spacer layers; and

FIG. 7 is an enlarged section view of a portion of a fourth embodimentof the multi-layer optical data record without spacer layers.

DESCRIPTION OF PREFERRED EMBODIMENT

As shown in FIGS. 1 and 2, a multi-layered optical data record 10 of thereflective type, such as that shown in FIG. 4 which employs lightreflecting material for the data spots or for the background regionssurrounding transparent data spots, is played back with a playbackapparatus including a light source 12 and a light detector 14 positionedon the same side of the record. This reflective playback apparatus hasthe advantages of providing a more compact apparatus and enabling theuse of at least some of the optical elements including the objectivelenses 16 in the same light paths for the light reflected from therecord 10 to the detector 14 and for the light transmitted from source12 to the record. This reduces the cost and causes some of the defectsof the optical system, such as lens aberration, to be cancelled as aresult of the light beam traversing the elements twice in oppositedirections.

The light source 12 may be a laser which produces "coherent" light ofone or more narrow frequency bands, or a suitable source of intensenoncoherent "white" light of many frequencies, including ultravioletlight, infrared light, as well as visible light. A light beam 18 istransmitted from source 12 through a primary lens 20 and an aperturedlight mask commonly referred to as a "pin hole" element 22. Lens 20focus the light beam to a small spot at the circular aperture of the pinhole element so that such aperture shapes the light spot and forms theobject that is imaged onto the record by the objective lenses 16. Thelight beam 18 is transmitted through a beam splitting mirror 24 onto arotating distributor mirror member 26 whose outer surface is in the formof a five-sided polygon having five mirrors provided thereon whichcorrespond to five objective lenses 16 which are carried on a rotatingscanner wheel 28. The distributor mirror member 26 is mounted on theshaft 30 of the scanner wheel 28 so that it is rotated with such wheelat a constant speed by an electrical motor 32 coupled thereto. As aresult, the distributor mirror member 24 rotates at the same speed asthe objective lenses 16 so that one of the mirrors of such distributormember is always aligned with its associated objective lens. Thus, thedistributor mirror member 26 distributes the light beam to the objectivelenses 16 one at a time as such lenses rotate across the record 10 toplayback one of the data track lines 35 on such record as shown in FIG.2.

The light beam 18 is reflected from one of the distributor mirrors ontoone of five objective mirrors 34 mounted on the scanner wheel 28immediately beneath each objective lens 16. As a result, the light beamis reflected from the objective mirror 34 through its associatedobjective lens 16 onto the multi-layer optical data record 10. The lightbeam is focused by lenses 20 and 16 to a small spot in a focus plane onone of the data layers of the record, such spot being of a diameterwhich is substantially the same size as the width of one of the datatrack lines 35 of data spots provided on such record.

A selection means is provided for moving the focus plane from one datalayer to another to selectively play back the selected data track onsuch layers. This change in the focus plane may be accomplished bymoving the pin hole light mask 22 and the primary lens 20 longitudinallyalong the beam axis by means of an electromagnetic coil 36 andassociated electrical control circuit. The coil 36 attracts or repels amagnetic armature 38 on which the pin hole mask 22 is mounted so that itand the lens 20 coupled thereto move toward and away from the record 10.A spring biasing element 40 may be used for mounting the pin hole lightmask 22 which resists the electromagnetic force of the coil 36 for moreaccurate adjustment of the mask. However, it should be noted that inview of the great distance of the light mask 22 from the record 10, themotion of the object formed by the pin hole in mask 22 relative to themotion of the light spot image in the focus plane is equal to the squareof the magnification which is approximately 10. Therefore, the mask 22must move about 100 times farther than the resulting movement of thefocus plane of the light spot on the record. This enables accurateadjustment of the focus plane which is required for selective playbackof one of the data layers in view of the extremely small distancesbetween data layers.

The light spot focused on the record is scanned along one line 35 of thedata track without overlapping adjacent track lines. This scanning in alongitudinal or "X" direction along the track lines is accomplished byrotation of the scanner wheel 28 at a speed of about 2500 RPM for a fourand one-half inches radius to the center of the objective lenses. Toscan from line to line in the transverse or "Y" direction, the datarecord 10 is moved slowly downward in the direction of arrow 41 in anysuitable manner, such as by a worm gear apparatus 42 which moves acarriage 44 supporting the record and is suitably geared to the motor32. The speed of longitudinal movement of the record 10 is about 420microns per second for playing back a television signal on a record 5inches wide. As a result, each objective lens 16 scans a separate datatrack line 35 of the data track on one data layer of the record 10 asthe scanner wheel 28 is rotated in the direction of arrow 43.

The scanning light beam 18 is reflected from the data spots or thesurrounding background as a modulated readout light beam back throughthe objective lens 16 to the objective mirror 34 and distributor mirror26 to the beam splitter mirror. The beam splitter mirror 24 reflects themodulated readout light beam 46 to the detector 14 which is aphotoelectric cell that produces an electrical output signalcorresponding to the modulated light beam. This electrical readoutsignal is transmitted to the video input of the television receiver orother utilization device connected to the output of the detector througha suitable amplifier and decoder system (not shown).

A "tipping" plate 45 which laterally displaces the light beam 18 byrefraction of such beam is provided between the pin hole mask 22 and thebeam splitter mirror 24. The tipping plate is pivoted by a galvonometertype motor 47 in response to a tracking signal applied to its input forchanging the magnitude and direction of the lateral displacement of thelight beam 18 in order to cause such beam to stay on the data trackbeing scanned. The tracking signal is produced by a servo systemconnected to the output of the detector 14 as is shown in copending U.S.patent application Ser. No. 481,131, filed June 26, 1974, by R. A.Walker.

It should be noted that the light beam 18 is not coaxial with thedistributor shaft 30 but strikes the distributor mirrors 26 at a slightback angle which is less than the angle between the reflecting surfacesof such mirrors and the shaft axis. As a result the reflected light beamrotates at a speed slightly less than that of shaft 30 and fullyilluminates the objective lenses with a substantially uniform intensityover the entire data line 35. This is necessary because if the lightbeam is parallel to the shaft axis when it strikes the distributormirrors 26, the reflected beam will rotate at the same speed as theobjective lenses. This would cause the objective lenses to beilluminated with only about one-half the beam intensity at theirswitching positions where the beam is transferred from one lens toanother by the distributor.

As shown in FIG. 4, one embodiment of the multi-layer optical datarecord 10 includes a record substrate or base member 48 of a suitableplastic material, glass, ceramic or metal, which may be light opaque forreflective type records or light transparent for light transmission typerecords. A plurality of data layers 50A, 50B, 50C and 50D are providedon one or both sides of the substrate member 48. The data layers areseparated by transparent plastic spacer layers 52 which may be made ofthe same material as the substrate member 48. Each of the data layershas a series track or parallel tracks of data spots 54 formed by spacedtrack lines 35 on the record, as shown in FIG. 1. The data spots areseparated by spaces and may represent binary coded digital informationor frequency modulated or pulse width modulated analog information.

The data layers 50A to 50D may be made of photosensitive material, suchas photographic film, in which case the spacer layers are provided asthe film backing. However, the data layers may also be made by othersuitable recording material including printing ink, in which case thedata spots 54 could be made of light opaque black material and thebackground made of transparent material for light transmissive typerecords. However, the data spots 54 may also be made of light reflectingmetal material formed by vapor deposition through a mask havingapertures corresponding to the data spots, or by etching through aphotoresist mask formed by exposure to a light image of the data spotsin a conventional manner such as is used to form etched electricalcircuit boards. The thickness of the spacer layers 52 is greater thanthe depth of focus of the objective lenses 16 so that when the lightbeam 18 is focused on one of the data layers, the remaining data layersare out of focus and do not block the light beam appreciably, as shownin FIG. 4. A protective layer 56 of transparent plastic is provided overthe outermost data layer 50A to provide protection against mechanicalabrasion of the data layers and to prevent the dust which settles on thesurface of the record from blocking light to the data layers, by spacingthe dust from such data layers. Thus, any dust which collects on theouter surface of the protective layer 56 is out of focus with respect tothe light spot focused on any of the data layers. For this reason, theprotective coating 56 may have a coating of about 10 mils while thespacer layers 52 may have a thickness of about 5 mils and the substratebase member 48 has a thickness of about 1/8 inch, depending upon thematerial used for such substrate.

When the record of FIG. 4 is of a light transmissive type record, thedata spots 54 are preferably made of light opaque material, while thesurrounding background areas of the data layers are made of lighttransparent material, as is the record substrate 48. This lighttransmissive type record may be played back by modifying the playbackapparatus of FIG. 1, as shown in FIG. 3. This, the light detector 14 ismoved to the opposite side of the record 10 from the light source 12 andaligned with the light beam transmitted through the record 10 by theobjective lens 16. An arcuate lens segment 58 is positioned between thedetector 14 and the record, such lens segment having a short focallength on the order of six inches and a field of view which covers theentire width of the record element 10, as shown in FIG. 3A, so that suchlens may be held in a fixed position during scanning. The arcuate lenssegment 58 is cut from a large circular lens shown by dashed lines 59 inFIG. 3A. It should be noted that the beam splitting mirror 24 iseliminated in the embodiment of FIG. 3.

While the selection means including coil 36 and its control circuit 37may be employed to change the focus of the light beam 18 onto differentdata layers in the playback apparatus of FIG. 3 just as in theembodiment of FIG. 1, another selection means consisting of a pluralityof different colored filters 60 and 62 equal in number to the datalayers is shown in FIG. 3. In this case, the light source 12 is not alaser, but a suitable source of intense "white" light of manyfrequencies, and the record element 10 includes data layers of differentoptical properties, such as different colored dyes or different coloredphotoluminescent materials, as shown by record 10' in FIG. 6.

The record 10' of FIG. 6 includes data layers 64A, 64B and 64C which aredirectly layered on each other without the use of spacer layers, similarto layers 52 of FIG. 4, between such data layers. This is possiblebecause selection of the data layers is not accomplished by changing thefocus plane, but by the color filters 60 and 62 in the selection meansshown in FIG. 3. As stated earlier, the data layers 64A, 64B and 64C areof different optical properties. Thus the data spots in the three datalayers may be made of different colored dyes including the subtractivewavelength dyes used in color photographic film or of different lightemission wavelength photoluminescent materials in plastic binder layers.The data layers 64A, 64B and 64C are of extremely small thickness on theorder of 0.1 mil or less, since they are all within the same field offocus of the light beam.

The filters 60 and 62 equal in number to the data layers are selectivelypositioned in front of the detector 14 by an electric motor 66 which maybe a step motor controlled by a suitable control circuit 68 for properlyindexing the filters which are carried on a rotating support plate 70attached to the motor shaft 72. The filters can be of the additive orband pass type which transmit light of the wave lengths blocked by thecolored data spots in the data layers which are formed of subtractive orband reject color dyes. The data spots of different colored dyes can beformed by multiple exposure and development of color photographic filmwith different colored light beams so that the data layers are providedby the different emulsion layers of such film. However, the data spotsof different photoluminescent materials may also be formed by printingor by photoresist etching techniques in a similar manner to the dataspots of the record of FIG. 4. Also, the record 10' of FIG. 6 can bemade as a reflective type record and used in the playback apparatus ofFIG. 1 if a reflective layer is provided between the substrate 48 andthe bottom data layer 64C in a similar manner to FIG. 5.

The record 10" of FIG. 5 is a reflective type record similar to that ofFIG. 4, except that the data bits 54 are made of light opaque material,and a light reflecting metal layer 74 is provided between the substrate48 and a spacer layer 52 beneath the bottom data layer. Thus, the record10" of FIG. 5 is a reflective type record even though neither the databits 54 nor the surrounding background material of the data layers is oflight reflecting material. Of course, the reflecting layer 74 can beprovided by the surface of the substrate if such substrate is made ofmetal, rather than plastic, which may be preferred for dimensionalstability.

A fourth embodiment of the multi-layered optical data record 10'" isshown in FIG. 7 to be of the direct layered type like that of FIG. 6,which does not use spacer layers between its data layers 76A, 76B and76C, but is formed differently than the embodiment of FIG. 6. Thus, thedata layers 76A, 76B and 76C in the record of FIG. 7 may be formed byevaporating the different colored dyes or photoluminescent material ofthe data spots through a mask, by mechanical printing or by using aphotoresist etching process. The lower data layer 76C is applied to thesurface of the substrate first, then the data layer 76B and finally theupper data. For this reason, the data layer 76B contacts layer 76C andthe surface of the substrate through holes in layer 76C in some places,while layer 76A contacts the substrate and both the other layers 76B and76C. These data layers are formed of materials of different opticalproperties similar to that of record 10' of FIG. 6, includingsubtractive color dyes or photoluminescent materials which emitdifferent colored light when struck by the readout light beam.

Selective readout of the data layers in the records of FIGS. 6 and 7 maybe accomplished simultaneously by using a plurality of detectors andassociated filters and providing beam splitting mirrors in a similarmanner to that disclosed in U.S. patent application Ser. No. 375,336,referred to above. On those records in which the data spots aretransparent and the surrounding background areas are opaque orreflective, it will be necessary to make the background areas partiallytransparent, for example approximately 50% transparent, so thatsufficient light can reach the lower data layer to enable playback.

The data layers 50 and spacer layers 52 of FIGS. 4 and 5 can be formedin separate sheets and glued together and to the substrate member by asuitable solvent for the plastic material. However, photographic filmstrips exposed with different data tracks and developed may be used asboth the data layers and the spacer layers since the latter are formedby the transparent film backing layers. The film strips are transmittedthrough a tank of glue or solvent and then attached to the substratemember and passed through pressure rollers prior to drying. It should benoted that color slide photographic film has a plurality of differentcolor emulsion layers which can be used directly as the data layers toform a record like that of FIG. 6, since chemical development andprocessing can be carried out through the upper layers. However, in thiscase, there would be multiple exposures of the film to different coloredlight beams to form the data tracks on the different data layers.Finally, it should be noted that for records using photoluminescentmaterial of different light emission properties to distinguish betweenthe data layers, the playback light beam may preferably be ofultraviolet light since most conventional photoluminescent materials aremore sensitive to ultraviolet.

It will be obvious to those having ordinary skill in the art that manychanges may be made in the details of the above-described preferredembodiments of the invention without departing from the basis of theinvention. Therefore, the scope of the present invention should only bedetermined by the following claims.

I claim:
 1. A multi-layered optical data record comprising:a base memberincluding a first side and a second side separated by the thickness ofsaid base member; a plurality of optical data layers on said base memberhaving optical data information spots recorded as a plurality of spaceddata spots thereon, including first and second data layers of differentdata provided on the same side of at least one of said first and secondsides of said base member; said first and second data layers beingcontiguous so that corresponding surfaces of said layers are separatedby a distance less than the thickness of said base member; and saidfirst and second data layers each having complete data recorded thereonso that only one data layer at a time is used to modulate readout lightand thereby produce a readout signal of the data in said one layer.
 2. Arecord in accordance with claim 1 in which the data spots are frequencymodulated or pulse width modulated analog information.
 3. A record inaccordance with claim 1 in which the data spots are digital information.4. A record in accordance with claim 1 in which the data layers havephotographically recorded data provided thereon.
 5. A record inaccordance with claim 1 in which the data layers include portions oflight reflective material.
 6. A record in accordance with claim 1 inwhich the data layers include portions of light opaque material.
 7. Arecord in accordance with claim 6 in which a light reflective surface isprovided on the side of the base member adjacent said data layers.
 8. Arecord in accordance with claim 1 in which a plurality of data layersare provided on both sides of said base member including third andfourth data layers on the other side of said base member.
 9. A record inaccordance with claim 1 in which the first and second data layers areseparated from each other by a spacer layer of light transparentmaterial.
 10. A record in accordance with claim 1 in which the first andsecond data layers are in contact with each other and are made ofoptically different materials.
 11. A record in accordance with claim 10in which the data layers are made of different colored dyes.
 12. Arecord in accordance with claim 10 in which the data layers are made ofdifferent photoluminescent materials.